In the video above, veteran photographer and National Geographic award winner Carsten Peter talks about exploring and photographing Vietnam‘s underworld inside the Sơn Đoòng cave, which is inside the country’s Phong Nha-Kẻ Bàng National Park, close to the Laos border.

The cave was discovered in 1991 by a local man named Hồ-Khanh, but locals were afraid of the cave because of a whistling sound a large, fast-flowing subterranean river made. According to Yahoo.com, it wasn’t until 2009 that a group of scientists from the British Cave Research Association conducted a survey of the cave, finding it is five times larger than the Phong Nha cave, which was previously thought to be the largest in Vietnam. Sơn Đoòng also beat Malaysia’s Deer Cave for the title of the world’s largest cave. Some news outlets have reported that in spots, the cave is large enough to hold a skyscraper. Amazingly, the explorers have just scratched the surface, and still don’t know all that lies in the cave’s depths.

Peter, who returned to the cave with husband-and-wife team Howard and Deb Limpert, who conducted the first expedition, captured many incredible images in depths of the cave and surrounding area. In his talk, Peter quotes Howard Limbert, who said, “to find a giant cave like [Sơn Đoòng] in Vietnam is [like finding] a previously unknown Mount Everest.” See it for yourself in the video above and on the National Geographic website.

This Photo of the Day is titled “Sunny Isles” and comes from Gadling Flickr pool member Bens640. The scene is of a typical beach in Florida’s North Miami and, looking around the weather map, some of you could use a warm-weather photo to focus on.

I lived in the Midwest for about half a century before relocating to Florida almost a decade ago and saw plenty of ice, snow, stupid people driving during that “first snow” and breath-robbing sub-zero winds.

With modern photo editing techniques, it’s often difficult to tell the real from the, well, embellished.

Today’s Photo of the Day was snapped by Flickr user Neil Marek with an iPhone during an airplane descent on George Bush Intercontinental Airport in Houston, Texas. Its vintage feel is courtesy of Snapseed, an easy-to-use photo editing software for the iPhone, iPad and desktops, which offers much of the functionality of fancy photo programs like Adobe Photoshop, but at a fraction of the cost.

Does it have the purity of an unedited photograph taken by a fancy DSLR camera? Maybe not. But it’s still a very cool image.

The Iranians love Ferris wheels. When I spent a month in Iran back in 1994 I saw them everywhere. The parks in the big cities had the big, brightly painted ones we’re familiar with in the West. Smaller towns and villages had more modest Ferris wheels, some small enough that they could be cranked by hand.

I saw dozens of them. The one that stands out most in my memory was in a dusty little roadside village I passed through while riding a bus. The village was nothing more than a few dozen houses lined up on either side of the highway. This was Iran, though, and so it had its own Ferris wheel. It was homemade out of unpainted boards and had four seats that looked like they were old footlockers. An old man was cranking it around and around for the little local boys and girls, who all had big smiles on their faces as they went up, around, down and up again.

While I only saw it for a moment, it remains one of my most vivid memories of Iran. I wish I could show you a photo but I was zipping by in a bus and so I never got the shot. Instead, here’s a photo Tracy Hunter took in India. This Ferris wheel is about the same size.

While we’re on the subject of travel photography, is there a shot you missed that remains stuck in your mind? Tell us about it in the comments section!